Certain governmental specifications, for example, Navy Standard 1399, require a power supply in which the third harmonic is within three percent of the first harmonic. The sum of the total harmonics are required to be within less than five percent of the first harmonic.
Ideally, the current would be in perfect phase with the voltage to provide a power factor of 1. As the current becomes more out of phase with the voltage, the power factor lowers.
Referring to FIG. 1 of the drawings, for example, the voltage sinusoidal wave 12 is input to a switching power supply. As a result of the large input capacitance seen by the input line into the power supply, the current waveform 10 is significantly out of phase with the voltage waveform 12. Current waveform 10 in effect represents the time that current is being drawn from the input other than for the purpose of charging the filter capacitors.
Therefore, it is an object of the present invention to reduce harmonic distortion so that the current waveform will be substantially in phase with the sinusoidal voltage waveform.
Other objects and advantages of the present invention will become apparent as the description proceeds.